• 한국산학기술학회논문지
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• 제8권4호
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• pp.733-737
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• 2007

본 논문은 MCPCB에 다수의 와트급 LED를 모듈화하여 조명기구로 사용함에 따라 발생하는 열을 해결하기 위한 제안이다. LED가 조명기구로 사용되려면 칩의 용량이 커야하며 이 결과 P-N접합부의 열이 증가하게 됨으로 이를 해결하기 위해 펠티어 소자와 방열판 그리고 Fan을 설치하여 온도변화특성을 측정하였다. 또한 부가적으로 냉각소자와 방열판을 접속하는 열전도판, 단열재, Thermal Grease에 따른 온도변화특성을 실험하였다. 그 결과 방열판의 종류 및 체적에 따른 온도 변화가 가장 중요한 요소로 나타났다. Fan의 on, off에 따른 온도변화는 최대 $18[^{\circ}C]$의 변화폭을 주었으며 부가적 재료들도 $2{\sim}3[^{\circ}C]$의 온도변화에 영향을 주어 무시할 수 없는 요소임을 확인하였다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.59-59
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• 2017

Rice (Oryza sativa L.) is the most important crop and its yield must be improved to feed the increasing global population. Recently developed high-yielding varieties with extra-large sink capacity often have a problem in unstable grain-filling. Therefore, understanding limiting factors for improving grain-filling and controlling them are essential for further improvement of rice grain yield. However, since grain-filling rate was determined by complex sink-source balance, the ability of grain-filling was very difficult to evaluate. Source ability for 'grain' was not only determined by the ability of carbon assimilation in leaves, but also that of carbon translocation from leaves to panicles. Sink strength was determined by the complex carbon metabolism from sucrose degradation to starch synthesis. Hence, to evaluate the grain-filling ability and determine its regulatory steps, the whole picture of carbon flow from photosynthesis at leaves to starch synthesis at grains must be revealed in a metabolite level. In this study, the yield and grain growth rate of three high-yielding varieties, which show high sink capacity commonly, were compared. Momiroman showed lower grain filling rate and slower grain growth rate than the other varieties, Hokuriku 193 and Tequing. To clarify the limiting point in the carbon flow of Momiroman, $CO_2$ labeled by stable isotope ($^{13}C$) was fed to three varieties during ripening period. The ratio of $^{13}C$ left in the stem was higher in Momiroman 24 hours after feeding, suggesting inefficient carbon translocation of Momiroman. More interestingly, $^{13}C$ translocation from soluble fraction to insoluble one in the grain seemed to be slower in Momiroman. To get the further insight in a metabolite level, we are now trying the $^{13}C$ labeling metabolome analysis in the developing grains.

• 설비공학논문집
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• 제25권12호
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• pp.641-646
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• 2013

The purpose of this study is to improve the cooling performance of single and cascade refrigeration systems using thermoelectric modules. The system consists of a heat sink, fan, and thermoelectric module. The operating parameters considered in this study include power distribution between the first- and second-stage thermoelectric modules, air flow, and variable condensing unit. The cooling capacity increased with decreases in the temperature difference between hot and cold surfaces, but decreased with increases in the condensing temperature. The COP decreased with increasing electric power of the thermoelectric module because of the increased Joule heat. The cooling performance improvement using the thermoelectric module is represented by the freezer temperature.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.39-46
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• 2014

A total loss of all heat sinks is considered a severe accident with a low probability of occurrence. Following a total loss of all heat sinks, the degasser/condenser relief valves (DCRV) become the sole means available for the depressurization of the primary heat transport system. If a nuclear power plant has a total loss of heat sinks accident, high-temperature steam and differential pressure between the primary heat transport system (PHTS) and the steam generator (SG) secondary side can cause a SG tube creep rupture. To protect the PHTS during a total loss of all heat sinks accident, a sufficient depressurization capability of the degasser/condenser relief valve and the SG tube integrity is very important. Therefore, an accurate estimation of the discharge through these valves is necessary to assess the impact of the PHTS overprotection and the SG tube integrity of the primary circuit. This paper describes the analysis of DCRV discharge capacity and the SG tube integrity under a total loss of all heat sink using the CATHENA code. It was found that the DCRV's discharge capacity is enough to protect the overpressure in the PHTS, and the SG tube integrity is maintained in a total loss of all heat accident.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권10호
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• pp.2357-2375
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• 2013

Message ferry is a controllable mobile node with large capacity and rechargeable energy to collect information from the sensors to the sink in wireless sensor networks. In the existing works, route of the message ferry is often designed from the solutions of the Traveling Salesman Problem (TSP) and its variants. In such solutions, the ferry route is often a simple cycle, which starts from the sink, access all the sensors exactly once and moves back to the sink. In this paper, we consider a different case, where the ferry route is a closed walk that contains more than one simple cycle. This problem is defined as the Closed Walk Ferry Route Design (CWFRD) problem in this paper, which is an optimization problem aiming to minimize the average weighted delay. The CWFRD problem is proved to be NP-hard, and the Integer Linear Programming (ILP) formulation is given. Furthermore, a heuristic scheme, namely the Initialization-Split-Optimization (ISO) scheme is proposed to construct closed walk routes for the ferry. The experimental results show that the ISO algorithm proposed in this paper can effectively reduce the average weighted delay compared to the existing simple cycle based scheme.

• 태양에너지
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• 제18권4호
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• pp.11-22
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• 1998

Floor panel heating system using hot water is the primary heating system of domestic residential building. This paper presents the results of performance analysis of the heat pump system with air source evaporator and single unit dual sink(SUDSk) condenser. The heat exchanger combines two separated condensers into a single condenser and the object of the SUDSk condenser is to release energy to dual sinks, i.e. air for air heating system and water for panel heating system in one single unit. Simulation program is developed for single unit dual source(SUDS) SUDSk heat pump system and some experimental data are obtained and compared with simulation results. Differences of heating capacity and COP in dual source operating mode are 7% and 8% respectively. Simulation results are in good agreement with test results. Therefore, developed program is effectively used for design and performance prediction of dual source dual sink heat pump system with SUDS evaporator and SUDSk condenser.

• 한국정밀공학회지
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• 제29권7호
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• pp.778-784
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• 2012

In comparison with some other light sources, LED has merits such as increased life expectancy, fast response, pollution free, and high energy efficiency. Lately, due to development of LED with high brightness and capacity, LED has widely used in many industrial fields such as automotive, aviation, display, transportation and special lighting applications. Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. In this study, experiments on measuring the heat generation rate of LED and the cooling performance of a heat sink were carried for analyzing the thermal characteristics of LED lighting system in free convection. From the results, dimensionless correlation on the cooling performance of heat sink in natural convection was proposed with Nusselt number and Rayleigh number as a guideline for designing cooling device of LED lightings.

• 전자공학회논문지
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• 제49권12호
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• pp.56-63
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• 2012

WBAN은 인체 내부 및 외부에 부착한 디바이스를 무선으로 연결하여 통신하는 근거리 무선통신 기술로 IEEE 802.15.6 TG BAN을 중심으로 물리, 데이터 링크, 네트워크, 응용계층에서 표준화가 진행되고 있다. WBAN 기술은 전력제한 및 생체특성을 반영하여 센서와 지그비 디바이스를 사용하여 에너지 효율적으로 구성한다. 무선 센서 네트워크는 다수의 센서노드와 센서노드가 전송하는 센싱 데이터를 수집하는 싱크노드로 구성된다. 센서노드는 넓은 지역에 정해진 형태 없이 배치되어 프로토콜에 의해 자가구성 능력을 가진다. 싱크노드는 고정 싱크노드와 모바일 싱크노드로 구분되고 모바일 싱크노드는 전체 네트워크의 에너지 소모를 분산시켜 고정싱크 노드보다 네트워크의 라이프 타임이 증가하는 장점이 있다. 센서노드의 제한된 에너지 자원은 WBAN의 에너지 효율측면에서 중요한 문제이다. 본 논문에서는 모바일 싱크노드 기반의 WBAN 환경에서 효율적인 데이터 전송을 위한 클러스터 토폴로지 알고리즘을 제안한다. 제안한 알고리즘은 그리드 기반의 라우팅 프로토콜 및 TDMA 기반의 스케줄링 알고리즘의 장점을 바탕으로 인접한 클러스터의 중첩영역을 최소화하고 클러스터 헤더의 데이터 부담을 감소시켜 수집지연 및 오버헤드가 빈번하게 발생하는 WBAN 환경의 무선 센서 네트워크에서 우수한 성능을 보였다.

• 소성∙가공
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• 제3권1호
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• pp.38-50
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• 1994

Fundamental deformation mechanism and plastic behavior of AISI304 austenitic stainless steel were investigated to evaluate press formability. Local and uniform deformation capacity of AISI304 steel were compared to those of ferritic AISI430 steel and Al killed low carbon steel. Nine kinds of austenitic stainless steels having different austenite stabilities were made in laboratory scale to examine the transformation behavior in various deformation mode and variation of mechanical properties. Deformation path and strain distributions along edge corner of commercial sink die were illustrated and effect of austenite stability on press forming of sink die was clarified with experiments using square cup drawing tools.

• 한국항공우주학회지
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• 제42권9호
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• pp.789-794
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• 2014

정지궤도급 차세대 통신위성에 탑재될 디지털신호처리기에는 디지털 고속통신을 위한 FPGA가 사용된다. 적용된 FPGA는 높은 열소산량을 가지고 있으며, 이로 인한 접합온도의 상승은 부하경감 요구조건을 만족하기 어렵고 장비의 수명과 신뢰도 저하의 주요 원인이다. 지상과는 달리 우주환경에서의 전장품의 열제어는 대부분 열전도를 통하여 이루어지고 있다. CCGA 또는 BGA 형태의 FPGA는 인쇄회로기판에 장착되지만, 인쇄회로기판의 열전도율은 FPGA의 열제어에 효율적이지 못하다. FPGA의 열제어를 위하여 부품 리드와 하우징을 직접 연결하는 히트싱크를 제작하였으며, 우주인증레벨의 열진공시험을 통하여 그 성능을 확인하였다. 높은 전력소모량을 가진 FPGA는 우주환경에 적용하기 어려웠으나, 히트싱크를 적용함으로써 부하경감 온도 마진을 확보하였다.